Cav3.3 is a calcium channel of the T-type that is involved in many brain processes. Contrary to other calcium channels Cav3.3 is activated by relatively low/negative voltages. Cav3.3 is not a classic cannabinoid receptor but its activity is modulated by cannabinoids. Since cannabinoids have a physiological effect on Cav3.3 it is effectively a cannabinoid receptor.
http://www.guidetopharmacology.org/GRAC/ObjectDisplayForward?objectId=537
http://en.wikipedia.org/wiki/CACNA1I
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References:
Pertwee, R.G., Howlett, A.C., Abood, M.E., Alexander, S.P.H., Di Marzo, V., Elphick, M.R., Greasley, P.J., Hansen, H.S., Kunos, G., Mackie, K., et al. (2010). International Union of Basic and Clinical Pharmacology. LXXIX. cannabinoid receptors and their ligands: beyond CB₁ and CB₂. Pharmacol. Rev. 62, 588–631.
Brain (cerebellum, occipital lobe, frontal lobe, amygdale, caudate nucleus, hippocampus > temporal lobe, putamen > substantia nigra, medulla). Isocortex, olfactory > striatum > cortical subplate, hippocampus > thalamus, hypothalamus, pallidum, midbrain, medulla. Soma and entire dendrite in cortical CA3, hippocampal and subicular neurons.
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